.\" Copyright (c) 2015 Mark Johnston <markj@FreeBSD.org>
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.Dd November 7, 2015
.Dt PHOLD 9
.Os
.Sh NAME
.Nm PHOLD
.Nd hold a process
.Sh SYNOPSIS
.In sys/proc.h
.Fn PHOLD "struct proc *p"
.Fn _PHOLD "struct proc *p"
.Fn PRELE "struct proc *p"
.Fn _PRELE "struct proc *p"
.Fn PROC_ASSERT_HELD "struct proc *p"
.Fn PROC_ASSERT_NOT_HELD "struct proc *p"
.Sh DESCRIPTION
The
.Fn PHOLD
macro increments the hold count of a process, and the
.Fn PRELE
macro decrements the hold count of a process.
.Pp
If a process with a non-zero hold count attempts to exit, it will sleep until
its hold count has reached zero before the kernel begins releasing resources
associated with the process.
Once a process has started exiting, it is invalid to increase its hold count.
Thus, callers must not attempt to hold a process that has the
.Dv P_WEXIT
flag set.
The VM daemon will not swap out the kernel stack of a thread belonging to a
process with a non-zero hold count.
.Pp
The
.Fn _PHOLD
and
.Fn _PRELE
macros are identical to
.Fn PHOLD
and
.Fn PRELE ,
except that they must be called with the process lock held.
.Sh AUTHORS
This manual page was written by
.An Mark Johnston Aq Mt markj@FreeBSD.org .
